Your son’s ECs are just fine. It shows involvement and commitment, not just checking a box and then doing nothing to get really involved. And he is doing something more than just going home and studying.
I do interviews for MIT and when I look at someone’s ECs, I like to ask what their role is in the activity. I hate to see laundry lists of ECs because there is usually no substance to their EC. There aren’t enough hours in the day for some of the lists I’ve seen (fortunately these are in the minority).
College is more than just classes and academics. There are clubs, sports and just having a social life. Part of the EC picture is: Can the applicant handle all the activities outside the classroom and still do well in the classroom.